Furnace vestibule having a movable ceiling



May 7, 1968 D. BEGGS FURNACE VESTIBULE HAVING A MOVABLE CEILING 2Sheets-Sheet l Filed Sept. 20, 1965 INVENTOR.' Bm; E s

BUNALD TTY May 7, 1968 D. BEGGS FURNACE VESTIBULE HAVNG A MOVABLECEILING 2 Sheets-Sheet 2:

Filed Sept. 20, 1965 wm mm INVENTOR.' .UNALB .H2555 BY WX ATTY.

United States Patent O 3,331,947 FURNACIE VESHBULE HAVlNG A MVABLECEILING Donald Boggs, Toledo, Ohio, assigner to Midland-RossCorporation, Toledo, (lllio, a corporation of Ullio Filed Sept. 20,1965, Ser. No. 433,675 Claims. (Cl. 2156-4) ABSTRACT 0F THE DESCLOSUREThis disclosure relates to furnace vestibules, and more particularly tofurnace vestibules having means for maintaining a predetermined gaspressure therewithin, whereby inert gases contained withinthe vestibulescan be subviected to a wide range of temperatures without such gasesbeing lost to the atmosphere. In an embodiment disclosed herein afurnace vestibule is provided with a ceiling having a movable portionthat is responsive to pressure changes. As the gases within a vestibuletend to expand when heated, the movable portion will respond to thechange in pressure and increase the volume of the vestibule, until suchtime as an equilibrium is achieved. Conversely, when the gases tend tocontract due to cooling, the movable portion will move in the oppositedirection to decrease the volume of the vestibule and maintain aconstant pressure therein. Thus, a means is provided to prevent loss offurnace atmosphere when gases expand in the vestibule and to prevent thedrawing in of air when gases contract therein.

In most heat treating furnaces it is necessary to maintain anon-oxidizing atmosphere during the heat treating of a workpiece orload. Rather than charge the load directly into the furnace, ordischarge the load directly into the atmosphere, means, such as avestibule, is usually provided whereby the load may be in anon-oxidizing atmosphere before being placed into and after removal fromthe heating chamber of the furnace, so that when. the chamber doorseparating the vestibule from the beating chamber is opened for chargingor discharging of the load, no air enters the heating chamber. Anon-oxidizing is usually supplied directly to the heating chamber andthe door of the heating chamber may be provided with an aperture so thata portion of the non-oxidizing gas is diverted to the vestibule, or thegas may be supplied to the vestibule through a by-pass means connectingthe vestibule to the heating chamber.

Throughout the heat treating cycle, the gas within the vestibuleexperiences pressure changes due to a variation in temperature. This isparticularly true when the chamber door is opened and the gas in thevestibule is quickly heated. At this time, the gas in the vestibuleexpands and a portion of it escapes into the atmosphere either throughcracks or small openings in the vestibule or through vent means providedfor release of pressure build-up. After the aforementioned door isclosed, the pressure in the vestibule drops, as a result of thedecreased temperature, and air is drawn into the vestibule through thesame cracks and small openings. Because of the presence of air in thevestibule, when a load is transferred from the same to the heatingchamber, a small portion of air also enters the latter. In most heattreating processes, the presence of a small amount of air is not harmfuland the atmosphere of the heating chamber can be controlled toaccommodate this small amount of air; however, present day heat treatingspecifications are becoming increasingly stringent with respect tocontrolled atmosphere requirements so maximum physical properties in thefinal product may be attained. To meet these more stringentrequirements, it is ICC sometimes necessary to utilize an inertatmosphere with a virtually complete absence of air during heattreating. In order to maintain a controlled atmosphere within theheating chamber, it is necessary to maintain a like atmosphere in thevestibule. It' inert gas is lost from the vestibule each time thechamber door is opened, the cost of supplying the inert gas would behigh, particularly if the inert atmosphere were argon. It would bedesirable from an economics point of view to retain all the inertnonoxidizing gas within the vestibule no matter what temperaturevariation may occur therein.

lt is, therefore, an object of this invention to provide a furnace witha vestibule wherein the atmosphere within the vestibule can be subjectedto a wide range of temperatures without such gases being lost to theatmosphere.

it is another object of this invention to provide a furnace vestibulewith a unique ceiling.

It is still another object of this invention to provide a ceiling whichis responsive to pressure variation.

It is a further object of this invention to provide a vestibule for afurnace wherein at least one of the walls of the vestibule is pressureresponsive :so that the volume within the vestibule is variable.

It is a still further object of this invention to provide a furnacevestibule capable of increasing its volume as the temperature of theatmosphere therein. increases, thereby maintaining a constant gaspressure therewithin.

In the drawing:

FIG. 1 is an elevated sectional view of a furnace ernbodying theprinciples of the invention. 4

FIG. 2 is a plane view of the furnace shown in FIG. 1 taken along theline 2 2.

In one embodiment of this invention, a furnace is provided with avestibule so that a non-oxidizing atmosphere may be maintained withinthe heating chamber of the furnace as a load is charged into or out ofthe furnace. The vestibule is provided with a floating roof which issupported by liquid sealing means. When the temperature of theatmosphere within the vestibule rises as a consequence of a furnace doorbeing opened, the roof rises in its seal, as a result of thermalexpansion of the gases, to increase the volume of the vestibule andmaintain a constant pressure therein. After the furnace door is closed,the temperature of the vestibule atmosphere decreases and the floatingroof descends to decrease the volume, thus assuring that no leakage ofair into the vestibule occurs and negating the necessity of having tosupply additional gas.

Referring now to the drawing, a furnace embodying the principles of thisinvention is shown generally at 1i) and comprises a heating chamber 12,an entrance vestibule 14 attached to one longitudinal end I5 of theheating chamber, an exit vestibule 16 attached to the other longitudinalend 17 of the heating chamber, and a quench tank 13 disposed immediatelybelow and extending laterally from the exit vestibule.

The heating chamber 12 has a refractory lining 2t) supported by a baseZ2 -upon which lining a refractory floor 24 is disposed. Extendingupwardly from the base 22 and formed with the ends 15 and 17 aretransversely extending side insulating walls 26 and 27. The enclosure ofthe heating chamber 12 is completed by an arched roof 28 of refractorybrick with a concrete covering 30 thereover. The end walls 15 and 17have openings 32a and B2b, respectively, therein, which openings provideingress and egress to the heating chamber 12. Longitudinally extendingon the chamber floor 24, substantially between the openings 32a and 32h,is a pair of rails 34, each rail being spaced and extending parallel tothe other.

The means for supplying heat to the heating chamber consists ofelectrical heating elements .36 (only one element being shown) whichextend longitudinally along the inside surface of the side walls 26 and27; however, any means for supplying heat may be employed as long as theatmosphere of the heating chamber is not contaminated by the type ofheat source employed. The atmosphere of the heating chamber 12 iscontrolled by gas inlets 37 and gas outlets 38 extending through theside walls 26 and 27.

Attached to the outside of each end 1S and 17 and about each opening 32aand 32b is a hollow metal casing 39 having a smooth outwardly exposedsurface 40. Disposed outwardly of openings 32a and 32b are verticallyslidable doors 41a and 41h, which doors separate the heating chamber 12from the entrance vestibule 14 and exit vestibule 16, respectively. Thedoors 41a and 41h are made of insulating bodies 42 having hollow metalframes 43 about the peripheries thereof. The inward facing 44 of thedoor frame 43 is smooth and adapted to engage the outside surface of themetal casing 39 when the doors 41a and 41b are in their lowest verticalposition, thereby sealing the openings 32a and 32b. Extending throughthe doors 41a and 4111 are apertures 47 that provide means for gas topass through the door.

Attached to the top of the door frames 43 are brackets 45 to which oneend of lifting rods 46 are secured. The other end of the lifting rods 46is engaged by means providing the necessary power to lift the door (theopposite end of the rods and the power means not being shown). The powermeans may be an electric motor, an air cylinder, or any other convenientmeans. Disposed above the door 41a and sealingly connecting the heatingchamber 12 and the entrance vestibule 14 is a metal hood 48 which actsas a guide for the door `41a as it is raised or lowered, as well ascontributing to the seal of the furnace 10. Attached to the lower endsof the door frames 43 are exible water lines 50 'which communicate withthe hollow interior of the door frames. Each water line 50 is slidablyreceived within a protective sheath 52 and is able to move with thedoors 41a and 41h as the latter are raised or lowered. Thus, means isprovided to circulate cooling water through the door frames 43 tomaintain the same at a relatively uniform temperature and preventwarpage of the door frames which would be caused -by temperaturefluctuation and lead to the loss of seal between the door frame and themetal casing 39. Means (not shown) is also provided for water coolingthe metal casing 39 for the same reason.

Sealingly attached to one longitudinal end 15 of the heating chamber 12is the entrance vestibule 14, comprising an insulating roof S4, a pairof longitudinal insulating side walls 56, a base 58 having a refractorytloor 60, and a vertically slidable outer door 62. Metal brackets 63extend between the heating chamber 12 to the walls 56 and base 58 of theentrance vestibule 14 to sealingly connect the vestibule to the heatingchamber. Sealingly attached to and supported by the vestibule roof 54 isa guideway 64 which is adapted to receive and guide the door 62 as itmoves vertically. One end of a lifting rod 66 is secured to the top ofthe door 62 by means of a bracket 68 and the other end of the rod isattached to power means for lifting the door (the other end of the rodand the power means not being shown).

Secured to the fioor of the entrance vestibule 14 is a second pair ofrails 69 which is longitudinally aligned with the first pair of rails 34of the heating chamber 12 and extends from the vestibule door 62 to theheating chamber door 41a.

Extending outwardly from the base 58 is a member 70 adapted to sealinglysupport the vestibule door 62 and to receive a longitudinal slidablepush rod 72 of sutiicient length to extend substantially into theheating chamber 12 when the door 41a is open. The push rod 72 isdisposed intermediate the rails 69 and has at its innermost end a loadengaging member '74 rotatably supported by a pin 76. The member 74 isoperative to approach a vertical position to extend above the rails 69when the push rod is moved inwardly toward the heating chamber 12 and itis adapted to assume a horizontal position as the push rod is slidoutwardly so as not to extend above the rails. Consequently, the member74 will engage a load placed upon the rails 69 to charge the same intothe heating chamber 12 as the push rod 72 is extended inwardly, but willnot engage a load on the rails during an outward stroke of the push rod.As shown in FIG. 1, the load 73 to be processed normally is placed in atray 75 and the member 74 engages the tray.

Attached to the side walls 56 of the entrance vestibule 14 are aplurality of electrical heating elements 78, and extending through thewalls are gas inlet means 80 and gas outlet outlet means 82. `Inaddition, a bypass means 83 having an orifice 84 therein, providescommunication between the heating chamber 12 and the entrance vestibule.Thus, when the vestibule door 62 is closed, the entrance vestibule issealed from the air, and the temperature and atmosphere within thevestibule may be controlled through cooperation of aperatures 47, gasinlet means 80, gas outlet means 82, and by-pass 83.

At the other end 17 of the heating chamber 12 is the exit vestibule 16and the quench tank 18. The quench tank 18 is immediately below andcommunicates with the exit vestibule 16. The quench tank 18 is supportedby a base 96 and has a portion 86 which extends laterally, the top ofwhich portion is open to the air. Metal sheeting SS sealingly connectsthe exit vestibule 16 to the heating chamber 12, and a hood is supportedby the vestibule and the heatin g chamber to form part of the sealingmeans therebetween and to slidably receive the door 4117.

The exit vestibule 16 has a floor extension 92 having a pair of rails 94which are aligned with the lioor 24 and rails 34, respectively, of theheating chamber 12.

The base 96 of the quench tank 18 supports a laterally extending railmeans 98 having a pair of laterally extending rails 100 and a pluralityof wheels or rollers 102 extending laterally in a longitudinally pairedrelationship. A framework 104 extends from the base 96 to the bottom ofthe exit vestibule 16 and is adapted to receive an elevator car 106which is operative, by means of a hydraulic motor 105, to movevertically within the framework and operative to be moved laterally uponthe rail means 98 by means of a push rod 99. The elevator car 106includes a carriage 107 adapted to rest upon the wheels 102 when the caris in its lowered position and a floor portion 1118 having a pair ofrails 110 thereupon, which oor portion and rails become aligned with theiioor 24 and rails 34, respectively, of the heating chamber 12 when theelevator car is in its uppermost vertical position. The rails 100 areprovided to guide the car 106 when the same is pushed on the wheels 102.

A puller rod 112 is sealingly received through the outside Wall 114 ofthe exit vestibule 16 at a position a short distance above andintermediate the paired rails 110. The rod 112 is adapted to extendlongitudinally into the heating chamber when the door -41b is open andhas, depending vertically from its inside end, a load engaging member116 rotatably supported by a pin 118. The engaging member 116 isoperative so that it is able to rotate counterclockwise when met by anobject, but it will not move from the horizontal position in a clockwisedirection. Thus, as the rod 112 is extended into the furnace 10, it ishigh enough to clear a tray 75 placed on the rails 34 of the heatingchamber 12, and the member 116 will engage the edge of the tray to berotated counterclockwise so that it is able to hook over the edge. Asthe rod 112 is pulled away from the heating chamber 12, the engagingmember 116 will engage the inside of the edge of the tray 75 and pull ittherealong.

The quench tank 18 is filled with uid 120 having low oxygen solubility.The longitudinal side wall 122a of the exit vestibule 16 adjacent thelateral extending portion 86 of the quench tank 18 extends into thequench tank immediately below the level of the uid, as indicated at 124,so that air is prevented from entering the exit vestibule. The otherlongitudinal side wall 122b extends downwardly to form a wall for thequench tank. Each wall 122e and 122b has gas inlet means 121 and gasoutlet means 123.

The roof 125 of the exit vestibule 16 has a circular opening 126therein. Attached to the roof 125 circumpositioned about the opening 126is an annular vessel 128 comprising a cylindrical inside wall 129 and acylindrical outside wall 13) which rise Substantially above thevestibule roof. The vessel 128 is tilled with a duid 132 having lowoxygen solubility, which fluid may be the same as used in the quenchtank 18.

Disposed within the center of the annular vessel 122 is a drum shapedceiling member 134 having a hollow cylindrical portion 136 and a diskportion 138, which disk portion forms part of the ceiling of the exitvestibule 16. A ring 140 is attached intermediate the ends of thecylindrical portion 136 and circumferentially exceeds intermediate thewalls 129 and 130 of the vessel 128. Depending from the outsidecircumference of the ring 141) and into the uid 132 is a cylinder 142having a length slightly less than the height of the vessel walls 129and 130. From the foregoing, it is apparent that the ceiling member 134is vertically movable but will maintain the gastight integrity of theexit vestibule 16 regardless of the vertical position of the member.Although in this particular embodiment an annular vessel 128 and drumshaped ceiling member 134 are used, it is obvious that any convenientconfiguration, such as rectangular, may be used without departing fromthe scope of the invention.

To aid the mobility of the ceiling member 134, a frame 144 is providedtovertically guide the member and prevent it from becoming tilted againstthe inside vessel wall 129. The ceiling member 134 is provided withframe 144 engaging wheels or rollers 146 to facilitate vertical movementof the member, and a counterweight 143 is connected to the ceilingmember through a line 150 attached to a bracket 152. An annular member153 is secured near the top of the frame 144 to limit the verticalmovement of the drum 134.

In the operation of the furnace 10, all the doors 41a, 41h, and 62 areclosed and the heating chamber 12 is raised to the operating temperaturethrough the use of the beating elements 36. When the proper temperatureis obtained, an inert atmosphere, such as argon, helium, or the like, isintroduced into the heating chamber 12 through the inlet pipes 37 andthe chamber is purged in cooperation with the outlet pipes 38. A slightpositive pressure is maintained within the chamber 12 and gas flowsthrough apertures 47 into the vestibules 14 and 16.

After the heating chamber 12 is at the proper tempera ture and has aninert atmosphere, the entrance vestibule 14 is heated to a temperatureintermediate room temperature and the temperature of the heating chamber12. This intermediate temperature of the entrance vestibule is termedthe preheattemperature and is used to increase the temperature of theload to be charged to an intermediate point so that it will notexperience thermal shock when it is placed into the heating chamber 12.In addition, by maintaining a preheat temperature, a smaller quantity ofgas is required to supply an inert atmosphere to the entrance vestibule14. After the entrance vestibule 14 is raised to the proper temperatureby the heating elements 78, the door 62 is opened and a tray 75containing a rst load 73 is placed upon the rails 69. The door 62 isthen closed and an inert atmosphere is introduced into the entrancevestibule 14 through utilization of the outlet means `82, in cooperationwith the apertures 47 and/ or the inlet means titl. At this time aninert atmosphere can also be admitted to the exit vestibule throughcooperation of the gas outlet means 123 with the apertures 47 and/or thegas inlet means 121. Suicient inert gas is supplied to the exitvestibule 16 to provide enough pressure to barely support the ceilingmember 134.

tit

With an inert atmosphere in the entrance chamber, the door 41a may beopened preparatory to charging` the load '73 into the heating chamber12. With the raising of the door 41a and the fact that the temperaturewithin the heating chamber 12 is substantially higher than thetemperature of the entrance vestibule 14, there will be expansion of thegases within the vestibule and a portion of the gas may be vented outthe outlet means 82. The load 73 is charged into the heating chamber 12by pushing the push rod 72 inwardly until such time as the load engagingmember 74 engages the tray 75 and pushes the same into the chamber. Thepush rod 72 is then removed from the heating chamber 12 to its outermostposition, and the chamber door 41a is closed. At this time, thevestibule door 62 is opened and a second load is placed within theentrance vestibule. The vestibule is purged of air by means of the gasinlet Sil and gas outlet 82, after which a small positive pressure ofapproximately 0.5 W.C. gauge is maintained by means of the by-pass 32communicating the vestibule 14 to the heating chamber 12. This smallpositive pressure prevents leakage of air into the entrance vestibulewhile the rst load is being heat treated in the chamber 12.

The charge 73 remains in the heating chamber 12 sufficiently long tocomplete the heat treating cycle. At this time the elevator car 1% ismoved to its uppermost position in the exit vestibule 16 and the ceilingmember 134 is in a vertically downward position so that Ithe ring 141)virtually rests on the upper edge of inner wall 129 of the vessel 129,and an inert atmosphere resides within exit vestibule 16. With thecompletion of the heat treating of the load, the second chamber door @1bis opened, and, as a consequence, the temperature of the inert gaswithin the exit vestibule 1e increases. With the increase in thetemperature, the pressure of the inert gas tends to increase due tothermal expansion of the gas. As the gas pressure tends to increase, thesealing member 134 begins to rise to bring an equilibrium in thepressure of the gas within the vestibule 16. More particularly, when thegas is at a given pressure, it will have suiicient energy to overcomethe weight of the ceiling member 134 and cause the same to be suspendedwithin the vessel 12S. As the temperature of the gas increases, thermalexpansion causes the ceiling member to rise until equilibrium isattained between the weight of the member and the pressure of the gas.Thus, the gas pressure within the exit vestibule 16 remains constant asthe temperature varies therewithin. The ceiling member 134 will rise inproportion to the change of temperature, but suflicient volume increaseis provided within the space defined by the inside wall 129 so that theceiling member would not be completely lifted out of the vessel 1311. Asa safety measure, the annular member 153 is provided to restrict theupward movement of the drum. lt will be observed that the gases may owbetween the ceiling member 134 and the inside wall 129 of the vessel 128but the presence of the uid 132 prevents the gas from escaping out ofthe exit vestibule 16 and into the atmosphere. This same iiuid 132prevents air from passing between the outside wall 12@ and the cylinder129 to enter into the exit vestibule 16.

After the door is opened7 the puller rod 112 is extended into thefurnace 1) until the engaging member 116 passes over the tray 75. Therod 112 is then pulled back and the engaging member 116 will engage theinside surface of the tray 75, thereby causing the tray to be pulledback along-the rails 34 on the base 24. The` tray '75 is pulled backalong the rails 34, 94 and 116 until such time as it rests substantiallyin the center of the elevator car 1116. At this point, the elevator car1116 with its load 73 is lowered through the framework 11141 by themotor until it rests upon the rail means 9S at the bottom of the quenchtank 18. As the elevator car 106 is lowered, the tray 75 is disengagedautomatically from the member 116, and the charge is quenched as it islowered into the fiuid 132. The elevator car 106 is thus placed upon therail means 98 and it can be pushed by the push rod 99 toward theextending portion 86 of the quench tank. From this position the trays 7Smay be lifted out of the quench tank and into the atmosphere inasmuch asthey have been reduced in temperature sufiiciently so that the charge'73 will not be at a temperature where it would oxidize.

With the removal of the load 73 from the exit vestibule 16, the door 1bis closed. With the closing of the door L11b the temperature of theinert gas within the exit vestibule 16 will reduce substantially,causing a decrease in the pressure of the same. As a consequence, theceiling member 134 will now fall within the vessel 128, and the ring 14dwill approach the top of the inside wall 12.9. Thus, the exit vestibule16 has gone through a complete cycle of providing egress means for acharging load from the heating chamber 12, whereby the atmosphere withinsuch exit vestibule has been conserved, and no need has arisen forsupplying new atmosphere or for venting any therefrom.

In the first embodiment, a liquid seal in the form of a vessel 128 wasused as a means for providing gas expansion. It is obvious that othermeans may be used equally as well. For example, rather than having aliquid seal, -the cylinder 142 and fluid 142 may be replaced by acollapsible and expanding member such as an accordion type structure. Inthis way the gasses overcome the weight of the ceiling member 136through thermal expansion as in the example of the liquid seal. Themember will provide expanding means for the ceiling member while stillmaintaining the seal within the vestibule.

Although gas saver 127 was provided in the exit vestibuie 16 in thefirst embodiment, it is obvious that a gas saver of this type may beplaced in another part of the furnace and still accomplish the objectsof this invention. For example, the gas saver 127 may be placed on thehood 3() of the heating chamber 12 and still maintain a predeterminedpressure. The presence of the apertures d'7 in the door 41b render theheating chamber 12 and exit vestibule 16 confluent to one another,thereby equalizing the pressures therebetween. With this construction,the increase in pressure in the exit vestibule 16, when the chamber door1b is open, would cause the ceiling member 134 to rise in the roof 28 ofthe heating chamber 12. After the door is closed and the gases withinthe exit vestibule 16 tend to contract, the gases within the heatingchamber 12 would pass through apertures 47 to compensate for the loss inpressure and gas volume in the exit chamber 16. Although it is possibleto place the gas saver within the heating chamber 12, this is notpreferred because of the complex structure of the heating chamber roof3f) as compared to the ceiling of the exit vestibule 16.

It would also be possible to place the gas saver at a distance from thefurnace. For example, an expandable chamber, built in accordance withthe principle heretofore described, could be placed at a distance fromthe furnace and made confluent with the latter through means such as apipe. In this way the expandable means may be introduced to any part ofthe furnace without materially yinterfering with the normal furnaceconstruction.

I claim:

1. A furnace for heat treating a load, comprising first wall meansdefining a longitudinally extending heating chamber having first andsecond opening means each at a longitudinal end of said chamber, heatingmeans disposed within said `heating chamber, second wall means definingan entrance vestibule contiguous with a longitudinal end of said firstwall means and having load access means, load moving means associatedwith said second wall means operative to move a load from said entrancevestibule through said rst opening means and into said heating chamber,third wall means defining an exit vestibule contiguous with the otherlongitudinal end of said first wall means and having a ceiling with anopening therein, a quench tank contiguous with said exit vestibule andhaving a liquid therein, said liquid communicating with the atmosphere,load moving means associated with said third wall means and operative toremove a load from said heating chamber through said second opening andinto said exit vestibule, means disposed within said quench tank forremoving a load from said exit vestibule into said quench tank,receiving means disposed upon said ceiling and circumpositioned aboutsaid ceiling opening, a ceiling member slidably disposed within saidreceiving means in a sealing relationship and sealingly covering saidceiling opening, and means for supplying a nonoxidizing atmosphere tosaid chamber and to at least one of said vestibules, said ceiling memberbeing operative to slide within said receiving means in response totemperature change of said non-oxidizing atmosphere within said exitvestibule.

2.. A furnace for heat treating a load, comprising first wall meansdefining a longitudinally extending heating chamber having first andsecond opening means each at a longitudinal end of said chamber, heatingmeans disposed within said heating chamber, second wall means definingan entrance vestibule contiguous with a longitudinal end of said firstwall means and having load access means, load moving means associatedwith said second wall means operative to move a load from said entrancevestibule through said first opening means and into said heatingchamber, third wall means defining an exit vestibule contiguous with theother longitudinal end of said first wall means and having a ceilingwith an opening therein, a quench tank contiguous with said exitvestibule and having a liquid therein, said liquid communicating withthe atmosphere, load moving means associated with said third wall meansand operative to remove a load from said heating chamber through saidsecond opening and into said exit vestibule, means disposed within saidquench tank for removing a load from said exit vestibule into saidquench tank, liquid containing vessel means disposed upon said ceilingand circumpositioned about said ceiling opening, a ceiling memberslidably received within said vessel means in a sealing relationship andsealingly covering said ceiling opening, and means for supplyingatmosphere to said heating chamber and to said vestibules, said ceilingmember being operative to slide within said vessel means in response totemperature change of said atmosphere within said exit vestibule.

3. A vestibule for attachment to one end of a furnace, which end hasaccess means therein, comprising a base attached to the furnace end, apair of side walls spaced relative to one another and attached to thebase and to the furnace end, a back wall spaced relative to the furnaceend and attached to said side walls and to said base, vestibule accessmeans associated with said base, a ceiling member attached to thefurnace end and to said walls and having an opening therein; an annularvessel disposed upon said ceiling member circumpositioned about saidopening and comprising an enclosure formi-ng inner wall and outer wallextending normal to said ceiling member, a fluid contained within saidvessel between said inner and outer walls, a drum member slidablydisposed within the spaced defined by said inner wall; the bottom ofsaid drum forming a portion of the ceiling of said vestibule, a ringsecured to and top circumposing said drum member and extendingintermediate said inner and outer walls, a cylinder depending from theperimeter of said ring into said fiuid, whereby said drum member isresponsive to change in gas pressure within said vestibule and operativeto maintain said gas pressure constant.

4. In a furnace, the combination comprising first wall means defining aheating chamber, vestibule defining second wall means contiguous withsaid first wall means and having first access means thereto, secondaccess means disposed between said first and second wall means, meansfor supplying a nonoxidizing atmosphere to said first and second wallmeans, pressure responsive means associated with one of said wall meansand operative to vary the volume of said wall means upon change intemperature of said non-oxidizing atmosphere, whereby said non-oxidizingatmosphere maintains a constant pressure.

5. The furnace of claim 4 wherein said second access means is provided'with a movable door.

6. The furnace of claim 5 wherein said movable door has an aperturetherein.

7. In a furnace, the combination comprising first wall means defining aheating chamber, vestibule defining second wall means contiguous withsaid first wall means, a quench tank contiguous with said second wallmeans and having a liquid therein, said liquid exposed to and sealingsaid second wall means from the atmosphere, access means disposedbetween said first and second wall means, means for supplying anon-oxidizing atmosphere to said first and second wall means, pressureresponsive means associated with one of said wall means and Operative tovary the volume of said one wall means upon change in temperature ofsaid non-oxidizing atmosphere, whereby said non-oxidizing atmospheremaintains a constant pressure.

8. The furnace of claim 7 wherein said second access means is providedwith a movable door having an aperture therein.

9. The combination of a furnace and expanding means, comprising firstwall means defining a furnace, second wall means defining expandingmeans and having an opening therein, means creating a continentrelationship between said furnace and said expanding means, saidexpanding means comprising receiving means circumscribing said openingand movable means sealingly and movably engaging said receiving means toform a seal for said opening, said movable means being suspended by aselected pressure within said expanding means and being operative tomove upon change of pressure within said furnace, thereby changing thevolume of said expanding means and restoring said selected pressureWithin said furnace.

1G. The combination of a furnace and expanding means, comprising firstwall means defining a furnace, second wall means defining expandingmeans, and means creating a continent relationship between said furnaceand said expanding means, said expanding means 4having a pressuresensitive portion operative to vary the volume of said expanding meansupon a change in pressure within the latter.

References Cited UNITED STATES PATENTS 1,371,800 3/1921 Marden 236-151,431,289 10/1922 Craig 236-15 1,876,960 9/1932 Kenworthy 266-42,033,398 3/1936 Rogers 236-45 2,231,635 2/1941 Nelson 236-45 2,262,25211/1941 Roland 236-45 2,440,065 4/1948 Ashton 13S-31 2,441,803 5/1948Duis et al. 236-15 2,589,811 3/1952 Holcroft 266-4 X 2,752,147 6/1956Besselman et al 266-4 2,776,134 1/1957 Wingate 266-4 FOREIGN PATENTS144,921 4/ 1931 Switzerland.

I. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.

